1. Field of the Invention
This invention relates to a process for the preparation of N,N'-(dimethyl) piperazine compounds such as N,N'-(dimethyl) piperazine and more particularly, pertains to an improved liquid phase catalyzed process for preparing N,N'-(dimethyl) piperazine compounds.
2. Description of the Prior Art
Piperazine compounds and N,N'-(disubstituted) piperazine compounds are well known, having established utility in a myriad of applications in the chemical as well as the food-related arts.
Many methods of producing piperazine are well known. In one method for piperazine synthesis, diethanolamine and ammonia are reacted at relatively high temperatures and high pressures, e.g., 1,700 to 1,850 psig, see, for example, U.S. Pat. No. 2,910,477. It has also been disclosed that N,N'-bis-(2-hydroxyethyl) piperazine can be produced by heating diethanolamine in the presence of a molar excess of a carboxylic acid containing eight or more carbon atoms. See, for example, German Pat. No. 1,002,359.
Additionally, it has been disclosed that N,N'-bis-(2-hydroxyethyl) piperazine can be produced by bimolecular dehydration of diethanolamine with certain inorganic acid catalysts and particularly phosphoric acid and acid salts. See, for example, U.S. Pat. No. 2,636,033.
Unexpectedly, it has been found that N,N'-(dimethyl)-piperazine compounds, including the N,N-(dimethyl) C-(alkyl) substituted) piperazines, can be produced from the readily available and easily obtainable corresponding monoethanolamine or C-lower alkyl substituted monoethanolamines and methyl alcohol. One outstanding feature of the instant invention resides in the simplicity and availability of the reactants. Another outstanding facet of the instant invention is the fact that the desired compound is achieved in a single process step whereas such desired N,N'-(dimethyl) piperazine compounds are usually produced via multi-step and complicated processes.